In recent years, an increase in communication speed is demanded in a radio communication apparatus as well. Therefore, in a radio communication system, the increase in communication speed is realized by increasing a transmission capacity using plural channels.
In a conventional technology for realizing the increase in communication speed using plural channels, plural channels are allocated and secured in advance in a path between a specific communication unit system and a specific terminal unit system, in which a wide transmission band is required, to perform communication on the plural channels (see, for example, Japanese Application Laid-Open Publication No. 2002-135304).
However, in the case of radio communication, communication state changes depending on environments like obstacles and weather conditions (e.g., rainy weather). In addition, in the case of mobile communication, a communication state always changes with time due to movements. In the conventional technology, a technique for selecting transmission systems and transmission speeds suitable for communication states in performing communication on plural channels is not disclosed. Therefore, there is a problem in that it is impossible to select a transmission system and a transmission speed suitable for a communication state in each channel.
For example, in the conventional technology, when a modulation system with a high transmission speed is adopted, although a transmission speed is increased, communication cannot be performed in a place where a state of a transmission channel is bad and retransmission requests increase, which results in decline in throughput. In addition, when a modulation system in which communication is possible even when a state of a transmission channel is bad, a communication speed falls, and an advantage of increasing a transmission capacity using plural channels is reduced.
The present invention has been devised in view of the above, and it is an object of the present invention to provide a radio communication apparatus that can select transmission systems and transmission speeds corresponding to respective channels in performing mutual communication using plural channels.